企业大多实行四班三运转，但是对于若干天之后自己上什么班却不好算，本程序以某一天为基准，然后算出任意时间前后哪一天应该上什么班，十分实用。-Most of the implementation of a total of four three-run enterprises, but for several days after the class was bad, what their calculation, the procedure for a particular day as refe